Digging into new MacBook’s support of GPU-accelerated H.264

Some Macs have shipped with video cards that support GPU-accelerated decoding …

H.264 is designed to rock everything from your crummy little mobile phone to that HDTV you probably shouldn't have bought. As anyone who has played H.264 video on a Mac or PC will tell you, though, H.264 also rocks even the most modern of CPUs, and hard. While the video cards in some recent Macs (desktops and notebooks alike) have supported GPU-acceleration of H.264, Apple may have released a special build of Mac OS X on its new MacBook line that actually takes advantage of this extra pair of GPU hands.

As Ars and MacRumors' forum users have noticed, the new MacBooks don't break nearly as much of a sweat when playing large H.264 files at 1080p. While previous generations (by no means slouches in the hardware department) can crank the CPU to 100 percent when playing a file, that same file appears to only require around 20-30 percent of the CPU on a new MacBook.

We know that NVIDIA's "PureVideo HD" tech in both of the MacBooks' new video cards (9400M for MacBook, dual 9400M and 9600M in MacBook Pro) is endowed with GPU-acceleration for a few heavy video codecs, including H.264. Older Macs, such as the previous generation of iMac and MacBook Pro (with the NVIDIA 8600GT), have also included GPU acceleration. But support for harnessing this tech wasn't on Mac OS X's menu until 10.6 Snow Leopard arrives next year with "QuickTime X."

But perhaps Apple is toying with releasing this tech a little early. In that same aforelinked Ars forum thread, astute readers noticed that Mac OS X on the new MacBooks includes a "QuickTime/AppleVAH264HW.component" file that isn't in the most current builds for other machines. The most current public version of Mac OS X Leopard is 10.5, build 9F33, but the new MacBooks are sporting 9F2114. While some of our readers have tried using this component on other Macs with video cards that support GPU acceleration, it's had no noticeable effect on QuickTime decoding performance.

All this leads to the theory that the new MacBooks are sporting a custom version of Mac OS X that finally harnesses GPU-acceleration for H.264 decoding (we can only hope this acceleration goes both ways). This wouldn't be the first time Apple has released new machines with a special build of Mac OS X, though. The MacBook Air got its own version in January (complete with a demo video that plays in the Mouse & Keyboard System Preferences pane) for its introduction of the multitouch trackpad.

This time around, though, Apple is in a different situation. The MacBook Air was the first Mac with hardware that supported multitouch trackpad gestures (Update: early 2008 MacBook Pros supported multitouch gestures as well), so multitouch wasn't something that Apple could bring to other Macs with a simple software update. But if the MacBook's special new version of Mac OS X 10.5.5 can indeed support GPU-accelerated H.264 decoding, and previous Macs have had the hardware built in for a while, we hope to see these features show up for the rest of us in 10.5.6.